Wire harness structure for matrix printing apparatus



May 9, 1967 R. c. BURNS ETAL WIRE HARNESS STRUCTURE FOR MATRIX PRINTING APPARATUS 18, 1965 2 Sheets-Sheet 1 Filed Oct.

INVENTOHS ROBERT C. BURNS TATSUO HASEGAWA VICTOR R. SIMPSON BY ATTORNEY 1967 R. c. BURNS ETAL 3,318,429

WIRE HARNESS STRUCTURE FOR MATRIX PRINTING APPARATUS Filed Oct. 18, 1965 2 Sheets-Sheet 2 United States Patent 3,318,429 WIRE HARNESS STRUCTURE FOR MATRIX PRINTING AIPARATUS Robert C. Burns, Conklin, Tatsuo Hasegawa, End'well,

and Victor R. Simpson, Owego, N.Y., assignors to International Business Machines Corporation, Armonk, N.Y., a corporation of New York Filed Oct. 18, 1965, Ser. No. 497,164 13 Claims. (Cl. 197-1) This invention relates generally to high speed printing apparatus and more particularly to the construction of a printing mechanism for use in a serial matrix printing machine.

Printing machines are known in which the outlines of characters are formed by printing the appropriate dots of a bi-dimensional dot matrix having the same general size as the characters to be printed. One version of such a machine, sometimes called a wire printer, employs a matrix of individually operable dot printing wire elements or the like which are projected in combination simultaneously against a platen to effect printing of the whole character on an interposed print medium. For printing a complete line of data, means are provided for effecting a relative longitudinal motion between the print matrix and the platen (and print medium) so that different characters are printed in series at successive positions along the print line.

In serial machines, the print head, having the Wire matrix former therein, is moved along the print line while the print wires are actuated successively to record the characters composing the line of print. The print head may be moved incrementally or continuously along the print line and then, upon completion of the line, returned to the starting point for the next line, usually at the left side of the record member. A characteristic of incremental motion is that the motion is interrupted so that one of the members moves in steps along the print line. It can be appreciated that if printing with incremental motion is to be performed at high rates of speed, the moving parts must be accelerated from rest, advanced, then brought to rest rapidly in short intervals of time. In addition, it is essential that the incrementing be performed at a high repetition rate. In the instances where the print head and its support are moved continuously along the print line, the print head must be oscillated on the moving support to eliminate relative motion between the head and record member at the instant of printing. The oscillatory motion thus required must also be at a high repetition rate.

The printing in a serial matrix printer is controlled by a stationary mechanism which projects the Wires required at each position along the print line. The print wires are contained in tubes arranged in rows and columns to form the matrix at the print head. The tubes and wires are suspended as a group between the print head support and stationary control mechanism. It is apparent that when the print head is moved incrementally or oscillated continuously the tubes are subjected to severe stress so that fractures occur due to early fatigue failure.

A partial solution to the problem of premature failure is to lengthen the Wires and tubes to increase the radius of curvature to decrease the stress level. The additional length, however, soon becomes impractical because of inertia and space requirements, and does not significantly extend the operating life. This is due to high stress concentrations still remaining at the print head support and control mechanism where rigid and flexible tube sections meet.

' control mechanism.

It is, therefore, a primary object of this invention to provide a harness for print wire tubes in a serial matrix printer which significantly improves and extends the life of print tubes.

Another object of this invention is to provide a flexible support for print wire tubes which prevents heretofore damaging stress concentrations.

A further object of this invention is to provide a sup porting harness for print wire tubes in a serial matrix printer which maintains large radii of curvatue and holds each tube free of damaging contact with another tube.

Yet another object of this invention is to provide a flexib-le harness for print wire tubes which holds all tubes in a common bending radius to prevent any one tube from being overstressed and to provide uniform support over a relatively large span.

A still further object of this invention is to provide a supporting harness for print wire tubes that is capable of damping vibration to thereby reduce tube strain.

The preceding and other objects are obtained in accordance with the practice of the present invention by providing a flexible harness to support the print wires and tubes as they are suspended between a print head and The print wire harness comprises a ribbon of resilient, flexible material having print tubes imbedded therein and held parallel so that each of the tubes could be intersected by a single straight line anywhere along their flexing length. This arrangement permits movement in a plane normal to the plane of tube support. The harness further has parallel flanges along each edge thereof, normal to the support plane of the tubes, forming a cross-section similar to an I-bearn. The harness is provided with ribs between the flanges transversely of the print tubes. The supporting ribbon or web of flexible material is formed with gradually increas- I ing thickness approaching the ends adjacent the print head and control mechanism to provide a gradually decreasing degree of flexibility to thereby eliminate sharp stress concentrations during bending of the print tubes. In order to form the print wires in a matrix at the print head, the wires and tubes adjacent thereto converge in a transition portion of the harness into a plurality of short parallel rows of tubes and thus form the two dimensional matrix required. The harness at the transition section is further provided with stiifening elements to limit bending stress variation and to prevent damaging relative motion between adjacent tubes. At the control mechanism end of the harness, the tubes extend beyond the end of the flexible ribbon to the control mechanism. There is thus formed between the print head and control mechanism a flexible harness for the print wires in which the degree of movement is limited substantially to a single plane.

The harness as used in the invention is readily adapted to molding techniques thus permitting inexpensive construction. The construction of the harness further eliminates the necessity of any intermediate support between the print head and control mechanism. The transverse ribs support the tube array, prevent collapse of the flanges, and protect the metallic tubes from damage. The invention greatly extends the print tube life by having graduated longitudinal flexibility so that the tube movement is limited in a desired manner.

The foregoing and other objects, features and advan tages of the invention will be apparent from the following more particular description of the preferred embodiment of the invention, as illustrated in the accompanying drawings wherein:

FIGURE 1 is a schematic diagram in perspective form of a serial matrix printer embodying the principles of the present invention;

FIGURE 2 is a perspective view of the print wire harness seen in FIG. 1 shown in greater detail; and

FIGURE 3 is a perspective View of the transition portion of the print wire harness adjacent the print head showing additional elements therein.

Referring to FIG. 1, the serial matrix printer apparatus comprises generally a stationary control mechanism Iii, a flexible print wire harness 11 including a matrix print head 12, and a recording medium 13. The print head is secured to a movable member such as a band 14 and is moved incrementally along a transverse supporting track (not shown) by any suitable mechanism such as electrostatic clutches 15, 16. At'each print position to which the print head is moved, the control mechanism is actuated by appropriate input signals to simultaneously project selected print wires through the harness and from the print head to produce the character desired. The wire ends move an ink'ribbon 17 against document 13 and platen 19 thus leaving an impression of a character on the document.

The print head movement is controlled by energizing the desired clutch or 16 to move the band 14 in the desired direction and for the distance requiredJ Stops 2G and limit switches 21 serve as auxiliary controls to ter- 'minate movement of the print head at each end of travel. 'The stops are adjustable to diiierent line lengths as may be required by the form to be printed. Primary positioning of the print head, however, is accomplished by other machine controls not shown. a

The print tube harness of the invention is shown in V greater detail in FIGS. 2 and 3. The harness may be con-' sidered generally as having -a terminal portion 25, intermediate portion 26, transition portion 27 and the print head 12. The intermediate portion may be defined as that portion in which the print tubes 28 are parallel and arranged so that each tube could be intersected. by a single straight line. In both the terminal and planar portions, the print tubes 28, having wires 29 therein, are arranged parallel to one another in a common plane. In the transition portion, the tubes converge from the intermediate array toward the print head and are formed into groups each having a common number equal to the. number of tubes in a vertical row in the character matrix concentrations in the print tubes and wires which heretoportion is covered with a relatively thick coating of mateat the print head. For example, the character matrix may be 'formed'by thirty-five print wires, arranged in a rectangle having five vertical, parallel rows each containing seven wires. Therefore each group of tubes in' the transition portion would have seven print tubes. The tubesin each group and the five groups are rigidly secured together, as by soldering, within the print head to form the rectangular matrix designated generally as 36 at theprint head. 7 V g The terminal portion 25 'of the harness is connected to a support plate 31 and arm'32that are in turn sup- 7 ported'by the stationary control mechanism 10; The

33 to abut the edge of a harness coating is notched at plate. 31 shown in phantom in FIG. 2. 1 A pair of clamps 34 and 35' are secured to arm32 and'tightenedagainst the harness to hold the terminal portion in place. The

harness tubes then fan out along plate 31 from clamp 35 to a point (not shown) where the print wires connect with the controlmechanisrn; The harness to the left of clamp 34 in FIG. 2 is thus free to flex as necessary to accommodate the tr-anslatory motion of print head 12 along the print line. It will be noted that clamp 34secures the harness at a point where there are flanges 4i and 41; by thus gripping the flanges, a limited degree of flexibility is permitted due to flange deflection.

The coating on the terminal portion of the harness is' molded with a gradually decreasing web thickness of the I-beam section from the point engaging clamp 35 to the intermediate portion of the harness. The gradual decrease in web thickness provides a corresponding gradual increase in the degree of harness flexibility. The gradual changein coating and flexibility eliminates sharp stress rial in order to severely limit oscillatory bendingstresses ,7 l and substantially eliminate any flexure of tube groups during the transition. Tube group overlap in the transition a portion produces high stress points which are aggravated by flexure and which tend to shorten the useful life. In order to assure practical rigidity, a pair of stifiening'elements 37 (FIG. 3) are embedded in the coating on oppo- 5 site sides of the converging tubes; The stifleners may be a metal or rigid plastic material'and extend substantially the'entire distance through which the print tubes converge. In addition to the elements 37 there is further included a pair of metal supports 38 the head and converging tubes havelittle, if any, flexibility and, therefore, have minimum oscillatory bending stresses It will be noted that the two sets of stifleners 37, 38 can be replaced with a single pair of longer supports.

Since the intermediate portion has the maximum harness flexibility and the converging portion of the harness is rigid, there is provided a gradual transition between the two limits of flexibility by fabricating the harness web with a coating having a graduated thickness. Thus from 7 the intermediate portion the coating thickness increases p in area 39 as shown in FIG. 3 through the point where the groups of print tubes start to converge andup to the maximum thickness near the print head. This portion. of the harness is'constructed similar to that at the terminal portion where the harness coating wasalso increased gradually. It will be noted in FIG. 3 that, because armed I V manner in which the harness is deflected, the transition portion of the harness and the part having the increased thickness are formed with a permanent curvature therein in order to accommodate the long interm'ediate portion. The long intermediate portion is necessitated by the length of line to be printed. V The harness is freely suspended between the stationary control mechanism 10 and the print head 12. Since the head moves in a horizontal path, the intermediate portion of the harness is mounted'in a curved vertical plane and normal .to the horizontal plane of head motion. Each.

tube is thus controlled to have an equal bending radius. The harness, however, must 'be given torsional stiffness between the control mechanism and head such that the vertical orientation is maintained at all times; This is accomplished by providing an upper flange 40 and lower flange 41 normal to the'plane of the harness web so that the harness has a cross-section similar to an I-beam. The flanges provide additional structure to share the .compression and tensile stresses and furnish the required torsional stiffness. The I-beam cross-section further promotes vibration damping by having the polyurethane alsosupported a substantial distance from the vertical neutral axis to absorb and reduce vibration. To insure that the print tubes remain in vertical alignment along the intermediate portion there are incorporated vertical ribs 42 in terconnected with the flange and web. The ribs are also embedded in the transition portion but extending therefromalong oppo- 1 a site sides of the print head 12. The latter supports help. in forming a rigid coupling between the print head'and spaced at predetermined intervals along the harness and are located in pairs on opposite sides of the harness web.

The harness is preferably formed by molding a resilient, semi-flexible coating material over the print tubes in the configuration desired. The tubes may be held in the arrangement required then sprayed with a liquified form of the polyurethane which then solidifies. A suitable material is M-86, a product of Spencer Chemical Corporation. The coating maintains the tubes and stifieners in their relative positions so that they can then be placed in a mold having the desired configuration. In the mold, castable polyurethane can be poured over the print tubes so that the flanges and ribs can be formed integrally with the web. Polyurethane has the desirable characteristic of dissipating energy.

It is preferable to mold a harness in a generally circular configuration to induce tube and coating stresses which are beneficial in damping oscillations caused by printing. The harness, when installed in the printer, is thus in a state of stress of varying amplitude depending on print head position. This stressed state increases the vibration energy absorbed by the polyurethane.

The incasing material for the print tubes should be considered for its inherent vibration damping, resistance to oil, and ability to be cast in the shape required. The product chosen for use was Adiprene L-100 a product of the E. I. du Pont de Nemours Company which is a liquid urethane rubber that can be converted into an elastic solid rubber. Other materials used should be either castable polyether polyurethane or polyester polyurethane, since these possess the required characteristics for assembly and operation. The hardness of these materials as indicated by a durometer is preferably within the rage of Shore A 65-95.

It will be noted that the harness is longer than the distance between the control mechanism and print head 12. The additional length of the harness has the advantage of permitting larger radii of curvature at the ex tremes of head travel so that the bending stresses remain 'below the allowable limit in the tubes. The additional length is limited, however, by the additional mass which must be incremented and in which vibrations must be damped.

The principles of construction in accordance with the invention have been embodied in a print harness having approximately nineteen inches of unsupported length. A typical cross-section of the web in FIG. 2 between flanges 40 and 41 in the planar portion was .031 inch thick. The over-all height of the harness was .906 inch to the outside of the flanges. Each flange cross-section at point D was .188 x .026 inch; at points C and E .188 X .035 inch; and at points B and F .188 x .045 inch. The web thickness gradually increased from .031 inch at point B to .440 inch at point A, and from .031 inch at point F to .165 inch at point G. Points A and G are approximately nineteen inches apart. The harness was constructed to accommodate a print tube matrix five tubes wide by seven tubes high so that thirty-five tubes were required with each tube having .015 inch outside diameter and .010 inch inside diameter. The tubes were composed of stainless steel.

A print harness fabricated as described above thus enables the construction of a high speed serial print device having significantly improved life characteristics. The harness has the advantage of a relatively low effective mass, and the print head end can be moved rapidly along the printing line and returned to a home position with minimized stresses. The construction further provides suflicient damping of vibrations that may be encountered during high speed operation and prolongs the practical life of the flexnral print harness.

If a broken print tube should occur, the harness assembly provides support for the temporary continuance of operation. When the molding material is sufliciently translucent, a tube fracture may be detected by the ac- 6 cumulation of ink which travels up the tube from the ribbon on a print wire.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a printing machine having print wires between a movable support at a printing line and a stationary print Wire control mechanism, a flexible harness for said Wires comprising:

a plurality of flexible, elongate elements arranged parallel to each other in an intermediate portion so that each element could be intersected by a single straight line and converging at one end thereof in a transition portion to form a rectangular character matrix securable to said support and having a connecting portion at the other end of said intermediate portion securable to said mechanism; and

a coating of resilient material incasing said elements for providing a unitary, flexible structure with said coating having gradually increasing thickness on said intermediate portion adjacent said transition and connecting portions to gradually decrease the flexibility thereof.

2. In a printing machine having print wires suspended between a movable support at a printing line and a stationary print wire control mechanism, a harness for said Wires comprising: a

a plurality of flexible, elongate tubes arranged parallel to each other so that each tube could be intersected by a single straight line, and each being connectable at one end portion to said support and connectable at the opposite end portion to said mechanism; and

a coating of resilient material incasing and binding said elements to form a unitary structure, with said coating having a gradually increased thickness over said elements in said end portions relative to said portion intermediate said end portions for gradually decreased flexibility thereof.

3. In a printing machine, a print wire harness comprising:

a plurality of elongate elements forming at one end thereof a rectangular character matrix and diverging therefrom through a transition portion to a portion wherein said elements lie parallel to each other and are arranged so that each element could be intersected by a single straight line; and

a resilient material incasing said elements in said transition portion by a first predetermined thickness and being gradually reduced therefrom to a second predetermined thickness at a selected distance from said transition portion along said parallel portion.

4. In a Wire printing machine having a support for print wires movable along a line of print and a stationary control mechanism for said wires, a flexible harness comprising:

a plurality of elongate, flexible elements arranged in a rectangular character matrix and secured to said support at one end thereof, and diverging through a transition portion to a portion wherein said elements lie substantially parallel to each other and are arranged so that each element could be intersected by a single straight line; and a resilient material incasing said elements having a relatively constant first thickness over said transition portion and gradually decreasing therefrom to a second thickness on said parallel portion a predetermined distance from said transition portion, to thereby provide increasing flexibility for said elements from said transistion to said parallel portion. 5. In a matrix printing machine having a plurality of print wires between a movable support at a printing line and a stationary print wire control mechanism, a flexible harness for said Wires comprising:

a plurality of flexible, elongate elements arranged at one end in a rectangular character matrix securable at said support and diverging therefrom in a transition portion to a parallel configuration in which said elements lie substantially parallel to each other and are arranged so that each element could be intersected by a single straight line, said parallel configuration extending into a portion attachable to said mechanism; coating of into a unitary structure with said material being gradually increased in thickness from selected positions on said parallel configuration and extending oppositely therefrom over said transition and attachable portions with sufliciently to establish rigidity in said transition and attachable portions; and e meanstto secure said matrix and attachable portions to saidrespective support and mechanism.

6. In a printing machine having print wires between.

a movable support at a printing line and a stationary print wire control'mechanism, a flexible harness for said wires comprising:

a plurality of flexible, elongate elements ararnged parallel to each other and arranged so that each element could be intersected by a single straight line, and converging therefrom through a transition section into a'rectangular character matrix securable to said support; and V a coating of resilient material incasing said elements for providing a unitary flexible structure, with said coating having gradually increasing thickness over an a ,7 end portion of the parallel elements and said transition section relative to said parallel elements, whereby said end portion has a varying degree of flexibili- 7. In a printing machine having print wires suspended between a movable support at a printing line and a stationary print Wire control mechanism, a harness for said wires comprising:

a plurality of flexible,

allel to each other so that each element could be intersected by a single straight line in an intermediate section, and each being connectable at one end portion to'said support and at the opposite end portion to said mechanism; and

a coating of resilient material incasing and binding said I elements to form a unitary, flexible structure having a varying thickness over said elements in said end portions relative to said intermediate section to produce a varying degree of flexibility in said end portions; V 1

8. In a printing machine having print wires suspended between a movable support at a printing line' and a stationary printwire control mechanism, a harness for said Wires comprising:

a plurality of flexible, elongate elements arranged parallel to each other in an intermediate section so 7 that each element could be intersected by a single straight line, and each being connectable at one end portion to said support and connectable at the opposite end portion to said mechanism; and

a coating of resilient material incasing and binding said elements to form a unitary structure, with said material being formed to provide a flange attached to an edge of said intermediate section and parallel with said elements therein.

9. Apparatus as described in claim 8 wherein said material is formed to provide a plurality of ribs projecting from said materialrin said intermediate section and each interconnected with said flange.

10. In a printing machine having print wires suspended resilient material binding said elements 7 said thickness being increased elongate elements arranged par-.

between a movable support at a printing line and a stationary print wire control mechanism, a harness for said wires comprising:

a plurality of flexible, elongate elements arranged parallel to each other so that each element could be intersected by a single straight line forming an intermediate section, and each being connectable at one end portion to said support and connectable at' a movable support at a printing line comprising:

a plurality allel to each other so that each element could be intersected by a single straight line in an intermediate section and converging at one end thereof'in a transition section to form a rectangular character matrix securable to said support and having a connecting" portion at the other end of said tion securable to said mechanism; and

a coating of resilient material incasmg said elements a for providing a unitary, flexible structure with said coating having gradually increasing said intermediate section over said adjacent transition and connecting portions, said materialrfurther being formed to provide a web about said intermediate section with flanges on opposite edges of a said web and normal thereto and parallel to said elements, said'coating having spaced ribs extending. between said flanges transversely of said elements; 1

12. In a printing machine having print wires between 0 a movable support at a printing line and a stationary print wire control mechanism, a harness for controlled flexibility, comprising:; 7 a

a plurality of flexible, elongate elements arranged parallel to each other so that each element could be intersected by a single straight section and converging at one end thereof'in a transition section to form a rectangular character matrix securable to said support and having'a connecting portion at the other end of said intermediate section securable to said mechanism;

means adjacent said elements in providing rigidity therefor; and

a coating of resilient material incasing sa d elements for providing a unitary strucand said rigidity means ture having'flexibility in said intermediate section, with said coating having gradually increasing thickness on said intermediate section adjacent saidtransition and connecting sections of said elements is gradually ative to said intermediate section. V, 13. In a printing machinehaving print Wires between a movable support at a printing line and a stationary print wire control mechanism, controlled flexibility, comprising:

a plurality of flexible, elongate means adjacent said elements in said transition section providing rigidity therefor;

on opposite edges elements, and further providing spaced ribs extendof flexible, elongate elements arranged par-,

intermediate sec-' thickness from said Wires, having 7 a line in an intermediate said transition section whereby said flexibility decreased therein rela harness for said w res having elements arranged parallel to each other so that each element could be ina matrix securable at said support and having'a con- 7 auxiliary members extending from said transition section to said movable support for providing a connection therebetween; and

a coating of resilient material incasing said element's, said adjacent means, and said auxiliary members for providing a unitary structure having flexibility in said intermediate section, with said coating having gradually increasing thickness on said intermediate section adjacent said transition and connecting sections whereby said flexibility of said elements is gradually decreased therein relative to said intermediate section.

References Cited by the Examiner UNITED STATES PATENTS Loop 1971 Wockenfuss 10193 Rast 197-1 X Braun et al. 197-1 X Leathers 1971 Fitch et a1. 197-1 10 ROBERT E. P'ULFREY, Primary Examiner.

E. S. BURR, Assistant Examiner. 

1. IN A PRINTING MACHINE HAVING PRINT WIRES BETWEEN A MOVABLE SUPPORT AT A PRINTING LINE AND A STATIONARY PRINT WIRE CONTROL MECHANISM, A FLEXIBLE HARNESS FOR SAID WIRES COMPRISING: A PLURALITY OF FLEXIBLE, ELONGATE ELEMENTS ARRANGED PARALLEL TO EACH OTHER IN AN INTERMEDIATE PORTION SO THAT EACH ELEMENT COULD BE INTERSECTED BY A SINGLE STRAIGHT LINE AND CONVERGING AT ONE END THEREOF IN A TRANSITION PORTION TO FORM A RECTANGULAR CHARACTER MATRIX SECURABLE TO SAID SUPPORT AND HAVING A CONNECTING PORTION AT THE OTHER END OF SAID INTERMEDIATE PORTION SECURABLE TO SAID MECHANISM; AND A COATING OF RESILIENT MATERIAL INCASING SAID ELEMENTS FOR PROVIDING A UNITARY, FLEXIBLE STRUCTURE WITH SAID COATING HAVING GRADUALLY INCREASING THICKNESS ON SAID INTERMEDIATE PORTION ADJACENT SAID TRANSITION AND CONNECTING PORTIONS TO GRADUALLY DECREASE THE FLEXIBILITY THEREOF. 